Diffusion of Zn along tilt grain boundaries in Al: Pressure and orientation dependence

For the first time, a systematic investigation has been carried out on the pressure and orientation dependence of diffusion along grain boundaries. Zn diffusion has been measured in the B-kinetic regime in different sets of A l bicrystals at 553 K. Pressures up to 1.2 GPa have been applied. Three set s of symmetrical < 001 >, < 011 > and < 111 > tilt grain boundaries have be en chosen with tilt angles around those, which correspond to a low coincide nce lattice site parameter. The Zn concentration depth profiles have been m easured by electron probe microanalysis and have been analysed using the Wh ipple equation. The orientation dependence of the diffusivity shows minima for the high coincidence grain boundaries at all applied pressures. Using k nown data for the bulk diffusion of Zn in Al, the activation volume for the triple product of grain boundary diffusion of Zn in Al has been determined for each grain boundary under investigation. The values of the activation volume range from 0.26 to 0.47 of the atomic volume of Al and show slight m axima for the high coincidence grain boundaries. (C) 2001 Acta Materialia I nc. Published by Elsevier Science Ltd. All rights reserved.